The present invention relates to a digital signal processor (DSP) installed in an electronic musical instrument or else for imparting a variable acoustic effect to a musical tone signal.
In the electronic musical instrument, the DSP carries out computation processings of a digital waveform of the musical tone signal to realize the acoustic effect such as echo. vibrato and so on. The DSP operates according to a given microprogram comprised of a plurality of computation steps. Conventionally, the DSP is provisionally set with fixed parameters or coefficients which are used in the respective computation steps.
Recently, it has been attempted to update the parameters of the DSP in real time basis in order to instantly vary the acoustic effect imparted to the tone signal during the course of musical performance. However, in order to update concurrently all the parameters used in a great number of the computation steps of the DSP, correspondingly a great number of registers are required and disadvantageously the operation of the DSP is complicated. Further, at the time of updating the parameters, the parameter values must be incrementally interpolated by an interpolator during a transient period in order to avoid sudden and irregular variation in the acoustic effect. However, in order to completely interpolate all of the numerous parameters. disadvantageously a large scale of the interpolator is required.